# Prediction of period, group and block of a given element

The period of an element corresponds to the principal quantum number of the valence shell.

The block of an element corresponds to the type of orbital which receive the last electron.

The group of an element is predicted from the number of electrons in the valence shell or/and penultimate shell as follows:

a)For s block elements ,group number is equal to the number of valence electrons.

b) For p block elements ,group number is equal to 10+number of electrons in the valence shell.

c)For d block elements ,group number is equal to the number of electrons in a (n-1) sub shell + the number of electrons in valence shell.

Question :Write the electronic configuration of the element with atomic number 29. Predict the period, group number and block to which it belongs.

Answer : Z=29 1s2 2s2 2p6 3s2 3p6 3d10 4s

Elements receive the last electron in the 3d orbital ,therefore, it belongs to d block elements and its group number = No. of electrons in the penultimate shell and valence shell = 10+ 1 =11

The period of the element = No. of principal quantum number of the valence shell = 4th